Wireless communication lines, connecting between a plurality of wireless communication devices, are each configured of a primary line and an overhead bit, wherein they may be degraded in wireless communication quality due to a reduction of a reception level via fading when an overhead bit includes a supervisory control line (i.e. an SV line). Patent Literature 1 discloses a wireless communication device having an adaptive modulation rate function (i.e. an AMR function: Adaptive Modulation Rate) which detects degradation of wireless communication quality so as to switch modulation to low-rate modulation, thus preventing line disconnection.
It is possible to adopt a wired network as a primary line, wherein due to the property of a wired network, congestion may occur due to the occurrence of a loop connection via a primary line. To prevent this problem, various devices (e.g. hubs, switches) configuring a network may adopt pathway control using STP (Spanning Tree Protocol) or RSTP (Rapid Spanning-Tree Protocol) so as to terminate redundant pathways, thus preventing a loop connection. There exists a technology defined by the Ethernet OAM (Operations, Administration, and Maintenance; IEEE802.1ag)/ITU-T Y.1731 such as ERP (Ethernet Ring Protection), wherein this technology needs a manual operation to perform an STP operation and is therefore limited in applied usage.
Patent Literature 2 discloses a technology for fixedly controlling communication pathways according to GMPLS (Generalized Multi-Protocol Label Switching). This technology needs to implement various device settings by manually designing networks, including auxiliary pathways, in advance.
Patent Literature 3 discloses a technology which aims to maintain predetermined data transmission speed and transmission quality even when wireless communication lines are degrading rapidly and which selects auxiliary lines so as to switch to a modulation scheme with low multiplicity, thus modulating and transmitting data signals.